Does anybody know if the usb port will only charge iPods via the cable?

I am asking because I got into the Google Music Beta and have been having a doozy of a time keeping my phone charged via the usb port. I am thinking it maybe a bad cable but only if it should be able to charge.

Thanks in Advance,

 

I've been able to charge an original iPhone and an iPhone 4, but not an iPhone 3G. Not sure if Apple changed the pinouts on the phones at some point or not.

 

I think it is 400mA max, which is probably not enough to power (let alone charge) a smartphone while streaming music over the air.

 

Thank You!

I am using a Droid 2, which I believe needs at least 500mA for a slow charge and closer to 850mA for a fast charge or charge and stream at the same time.

Car Charger time!